KR20090091156A - Travel drive device for working vehicle, working vehicle, and travel drive method - Google Patents

Abstract

A travel drive device for a vehicle has an HST drive device having a hydraulic pump driven by an engine and also having a hydraulic motor connected to the hydraulic pump by a closed circuit, an electric motor driven by using electric power generated by drive by the engine, a first drive wheel driven by the HST drive device, a second drive wheel driven by the electric motor, a vehicle speed detection section for detecting the speed of the vehicle, and a control section for distributing output of the engine to the HST drive device and to the electric motor such that, as the detected vehicle speed increases, the proportion of first power generated by the HST drive device reduces and the proportion of second power generated by the electric motor increases. ® KIPO & WIPO 2009

Description

Travel drive system, work vehicle and driving method of work vehicle {TRAVEL DRIVE DEVICE FOR WORKING VEHICLE, WORKING VEHICLE, AND TRAVEL DRIVE METHOD}

The present invention relates to a travel drive device for a work vehicle such as a wheel loader or a wheel hydraulic excavator, a work vehicle, and a travel drive method.

In this type of work vehicle, a hydraulic pump and a traveling hydraulic motor are connected in a closed circuit to form an HST traveling circuit, and the driving force of the traveling hydraulic motor is transmitted to the wheel through the propeller shaft to drive the vehicle. A traveling drive apparatus is known (for example, refer patent document 1).

[Patent Document 1]

JP-A-5-306768

However, the above-described traveling drive device can exhibit a great traction force at low speed travel due to the characteristics of the HST, but on the other hand, there is a problem that the transmission loss of the gear is increased at high speed travel, and fuel economy deteriorates.

A traveling drive device for a work vehicle according to the present invention includes an HST driving device having a hydraulic pump driven by a prime mover, a hydraulic motor connected to a closed circuit to the hydraulic pump, and an electric motor driven using electric power generated by driving of the prime mover. And a first drive wheel driven by the HST drive, a second drive wheel driven by the electric motor, a vehicle speed detector for detecting the vehicle speed, and an increase in the vehicle speed detected by the vehicle speed detector for distribution to the HST driver. And a control unit for distributing the output of the prime mover to the HST drive and the electric motor so that the ratio of the first power to be reduced and the ratio of the second power to be distributed to the electric motor is increased.

Instead of the electric motor, it is driven by using the electric power generated by the driving of the prime mover, and functions as an electric motor, and is driven by kinetic energy during driving, and installs a motor generator which functions as a generator, and accelerates / decelerates the vehicle. If a judging section for judging the output of the command is provided and it is determined that the acceleration command is output by the judging section, the motor generator functions as an electric motor, and is distributed to the HST drive unit as the vehicle speed detected by the vehicular speed detecting section increases. When the ratio of the first power to be reduced and the ratio of the second power to be distributed to the motor generator is increased, the output of the prime mover is distributed to the HST drive unit and the motor generator, and if it is determined by the determination unit that the deceleration command is output. The motor generator may function as a generator.

In this case, if it is determined by the determining unit that the deceleration command is output, the generation amount of the motor generator may be increased as the deceleration command value is larger.

An acceleration detection unit for detecting an acceleration command value is provided, and the power of the prime mover may be distributed to the HST drive and the electric motor so that the first power and the second power become larger as the acceleration command value becomes larger.

It is preferable to make a 1st drive wheel the front wheel, and a 2nd drive wheel the rear wheel.

In a range in which the vehicle speed detected by the vehicle speed detection unit is equal to or less than the first predetermined value, the ratio of the first power is controlled at a constant ratio larger than the ratio of the second power, and the vehicle speed detected by the vehicle speed detection unit is larger than the first predetermined value. Further, the ratio of the first power is gradually decreased in the range smaller than the second predetermined value larger than the first predetermined value, so that the ratio of the first power is adjusted in the range where the vehicle speed detected by the vehicle speed detection unit is equal to or greater than the second predetermined value. It can also be zero.

It may have a gear mechanism for transmitting power by the HST drive to the first drive wheels.

The output torque of the electric motor is kept constant until the traction force by the HST drive becomes zero, and the traction force by the electric motor starts to decrease after the traction force by the HST drive becomes zero by the increase of the vehicle speed. It may be provided with the torque control part which controls the output torque of a motor.

The traveling drive method of a work vehicle according to the present invention has a HST driving device in which a hydraulic pump driven by a prime mover and a hydraulic motor are connected in a closed loop, and the first driving wheel is driven by the HST driving device, and the first driving wheel is driven by the electric motor. Drives two drive wheels, and as the vehicle speed increases, the ratio of the first power to be distributed to the HST drive is reduced, and the ratio of the second power to the electric motor is increased.

According to the present invention, since the first drive wheel is driven by the HST drive device, the second drive wheel is driven by the electric motor, and the ratio of the engine output to the HST drive device is reduced as the vehicle speed is increased. The device can be operated efficiently and fuel economy can be improved.

1 is a side view of a wheel loader to which a traveling drive device according to a first embodiment of the present invention is applied;

2 is a diagram showing the configuration of a traveling drive device according to a first embodiment;

3 is a hydraulic circuit diagram showing the details of the HST travel circuit in FIG. 2;

Fig. 4A is a diagram showing the relationship between the pump tilt angle and the motor driving pressure of the hydraulic pump used in the circuit of Fig. 3, and Fig. 4B shows the motor tilt angle and the motor drive of the hydraulic motor. Degrees indicating the relationship between pressure,

5 (a) to 5 (c) are diagrams showing the characteristics of the traction force of the entire vehicle, the traction force by the HST drive device, and the traction force by the electric motor, respectively, which are obtained by the traveling drive device according to the first embodiment;

6 is a block diagram showing the configuration in the controller of FIG. 2;

7 is a diagram showing a relationship between traction and power;

8 is a diagram showing the configuration of a traveling drive device according to a second embodiment;

9 (a) to 9 (c) are diagrams showing the characteristics of the traction force of the entire vehicle, the traction force by the HST drive device, and the traction force by the electric motor, respectively, obtained by the traveling drive device according to the second embodiment.

[First embodiment]

EMBODIMENT OF THE INVENTION Hereinafter, 1st Embodiment of the drive system which concerns on this invention is described with reference to FIGS.

1 is a side view of a wheel loader which is an example of a work vehicle to which the traveling drive device according to the first embodiment is applied. The wheel loader 100 includes a front vehicle body 110 having an arm 111, a bucket 112, a tire (front wheel) 113, and the like, a cab 121, an engine chamber 122, a tire (rear wheel) 123. It is composed of a rear vehicle body 120 having a). The arm 111 floats by the drive of the arm cylinder 114, and the bucket 112 dumps or clouds by the drive of the bucket cylinder 115. FIG. The front body 110 and the rear body 120 are freely connected to each other by the center pin 101, so that the front body 110 to the left and right with respect to the rear body 120 by the expansion and contraction of the steering cylinder (not shown). Refraction The front wheel 113 and the rear wheel 123 are driven by the following driving drive apparatus, and a vehicle travels.

FIG. 2 is a diagram illustrating a configuration of a traveling drive device according to the first embodiment. The traveling drive device includes a front wheel drive device 10 for driving the front wheels 113 and a rear wheel drive device 20 for driving the rear wheels 123.

The front wheel drive device 10 includes a variable displacement hydraulic pump 11 driven by the engine 1 and a variable displacement hydraulic motor driven by hydraulic oil from the hydraulic pump 11. 12) The hydraulic pump 11 and the hydraulic motor 12 are connected to a closed loop to form a so-called HST running circuit. The rotation of the hydraulic motor 12 is transmitted to the front wheel 113 via the speed reducer 13 and the axle 14, and the front wheel 113 is driven by the HST traveling drive device. The reducer 13 has a gear mechanism that can be switched to a plurality of stages (for example, low / high).

Such an HST driving drive device (hereinafter simply referred to as HST) can exert a particularly large traction force during low-speed driving, so it is necessary to make the axle or propeller shaft a rigid structure for low gear so as to cope with traction force. The size and gear size tend to increase. For this reason, when the gear is shifted to the high gear and traveled at high speed, the transmission loss of the gear is increased, which leads to deterioration of fuel economy. Therefore, in this embodiment, the rear wheel drive apparatus 20 is comprised by the electric motor as follows, and the rear wheel 123 is driven by an electric motor at the time of high speed travel.

The rear wheel drive device 20 is driven by a generator 21 driven by the engine 1, a battery 22 that stores electricity generated by the generator 21, and electric power generated by the generator 21. The electric motor 23 and the inverter 24 which controls the drive of the electric motor 23 are provided. The rotation of the electric motor 23 is transmitted to the rear wheel 123 via the speed reducer 25 and the axle 26, and the rear wheel 123 is driven by the electric motor 23. The reduction gear 25 has a gear mechanism which can be switched to multiple stages (low / high) similarly to the reduction gear 13.

The inverter 24 is controlled by the control signal from the controller 50. The controller 50 is connected to a vehicle speed detector 51 for detecting the vehicle speed v and an operation amount detector 52 for detecting the operation amount A of the accelerator pedal. Based on the signals from these, the controller 50 controls the output torque T of the electric motor 23 according to the target output Pw2 (FIG. 6) of the motor 23 as demonstrated later.

Here, the configuration of the front wheel drive device 10 will be described in more detail. 3 is a diagram illustrating details of the HST traveling circuit. As shown in FIG. 3, the charge pump 15 is connected to the output shaft of the engine 1, and the throttle 16 is provided downstream of the charge pump 15. When the engine speed is increased by depressing the accelerator pedal (not shown), the discharge pressure of the charge pump 15 increases. The hydraulic oil from this charge pump 15 is guided to the light bulb cylinder 18 via the forward and backward switching valve 17, and the light bulb cylinder 18 is driven. As a result, the tilt angle qp of the hydraulic pump 11 increases with increasing engine rotation speed, the pump discharge amount increases, and the rotation speed of the hydraulic motor 12 increases. The forward and backward switching valve 17 is switched by a control signal from the controller 50 according to the operation of the forward and backward switching lever 19, and the flow direction of the hydraulic oil from the hydraulic pump 11 to the hydraulic motor 12 is changed. Controlled.

The pump tilt angle q changes not only by stepping on the accelerator pedal but also by the magnitude of the load acting on the hydraulic pump 11. For example, if the driving load increases while the engine 1 outputs full horsepower by maximizing the accelerator pedal, the engine speed decreases, the pump tilt angle decreases, and the pump discharge amount decreases. In this case, the relationship between the load (motor driving pressure P) and the pump tilt angle qp becomes as shown to Fig.4 (a). The characteristic f1-f3 of FIG. 4 (a) show the horsepower diagram with a constant power, respectively, and when the power Pw1 (FIG. 6) distributed by HST becomes small, a horsepower diagram becomes f1 → f2 → Shift as f3. In addition, the maximum value Pmax of the motor driving pressure is limited by a relief valve (not shown), and the maximum value qpmax of the pump tilt angle is physically limited by the structure of the pump itself.

In FIG. 3, the driving pressure P of the hydraulic motor 12 is guided to the tilt cylinder 12a, and the motor tilt angle qm changes according to the motor driving pressure P. In FIG. That is, when the motor drive pressure P becomes equal to or greater than the predetermined value Pa, the light bulb cylinder 12a is driven to the large light pole side, and as shown in FIG. It changes from the small diameter qm1 to the large diameter qm2. The light guide cylinder 12a is provided with an adjustment mechanism for adjusting the value of the predetermined value Pa by the excitation of the solenoid 12b. The predetermined value Pa is controlled according to the target power Pw1 of the HST by the control signal from the controller 50 described later. That is, when target power Pw1 becomes large, predetermined value Pa becomes large like characteristic g3-> g2-> g1.

F1 to f3 in Fig. 4A and g1 to g3 in Fig. 4B correspond to the same power Pw1, respectively. For example, the characteristic of the pump tilt angle qp when the power Pw1 is maximum is f1, the characteristic of the motor tilt angle qm is g1, and the predetermined value Pa is the maximum pump tilt angle (qpmax). Is set to be equal to the motor driving pressure P1 at the time of. As a result, when the driving load increases while the power Pw1 of the HST is maximum and the motor tilt angle is small (qm1), the motor tilt angle qm first increases to qm2 along the characteristic g1. The pump tilt angle qp decreases along the property f1.

5 (a) to 5 (c) are diagrams showing the relationship between the traveling speed v of the vehicle and the driving force (towing force) F. FIG. A of FIG. 5A is a characteristic of the traction force of the whole vehicle when the accelerator pedal is pressed down to the maximum. This characteristic a represents the traction force Fa of the whole vehicle when the vehicle is at full power, that is, when the engine 1 is outputting full power, and as the vehicle speed v increases, The pulling force Fa decreases. That is, since the power P of the vehicle is generally represented by P = F × v, when P is constant at the maximum power, the traction force Fa decreases as the vehicle speed v increases.

B1 and c1 of FIG. 5 (a) are the traction force Fb of the front wheel 113 by the front-wheel drive apparatus 10 (HST drive apparatus), and the rear wheel drive apparatus when the accelerator pedal is fully depressed, respectively. 20) It is a characteristic of the traction force Fc of the rear wheel 123 by the (electric motor 23), and when the characteristic b1 and the characteristic c1 are added, it becomes the characteristic a. In this embodiment, the characteristic of the traction force Fb of the front wheel 113, and the characteristic of the traction force Fc of the rear wheel 123 are set like FIG.5 (b), 5 (c). 5 (b) and 5 (c) show a plurality of characteristics b1 to b3 and c1 to c3 corresponding to the operation amount of other accelerator pedals. When the pedal operation amount is increased, the characteristic of the traction force Fb is b3 →. From b2 to b1, the traction force Fc changes from c3 to c2 to c1, respectively.

The characteristics b1 and c1 are characteristics when the accelerator pedal is pressed down to the maximum, respectively. When the accelerator pedal is pressed down to the maximum, as shown in Fig. 5 (b), the traction force Fb of the front wheel 113 is constant until the vehicle speed reaches v1, after which the Fb gradually decreases and the vehicle speed ( 0 in v2). On the other hand, as shown in FIG. 5 (c), the traction force Fc of the rear wheel 123 is constant until the vehicle speed reaches v2, after which the Fc gradually decreases and becomes zero at the vehicle speed v3. . In this way, by setting the vehicle speed v2 when the traction force Fb becomes zero and the vehicle speed v2 when the traction force Fc starts to decrease, the traction force Fa of the entire vehicle is smoothly adjusted according to the vehicle speed. The shock can be reduced.

In this embodiment, the output of the electric motor 23 so that the traction force Fb of the front wheel 113 and the traction force Fc of the rear wheel 123 may change according to the characteristic of FIGS. 5 (b) and 5 (c), respectively. The torque T is controlled. Moreover, the predetermined value Pa of FIG. 4 (b) is controlled. This point will be described below.

6 is a block diagram showing the configuration in the controller 50. In the target power calculating unit 58, the characteristics of the target power Pw1 of the HST drive device and the target power Pw2 of the electric motor 23 are stored in advance. These characteristics show how to distribute the engine output to the HST and the electric motor 23 according to the vehicle speed v. The total value Pw0 of Pw1 and Pw2 represents the power of the whole vehicle, and the power Pw0 is constant irrespective of vehicle speed v. In addition, since the engine output increases due to the increase in the operation amount A of the accelerator pedal, the target powers Pw1 and Pw2 are set to be larger as the accelerator pedal operation amount A becomes larger.

The target powers Pw1 and Pw2 are set to magnitudes corresponding to the vehicle speed v. That is, in the low speed region of v ≦ va, the target power Pw1 of the HST is set to be larger than the target power Pw2 of the electric motor 23. In the medium speed region of va <v <vb, the ratio of the target power Pw1 gradually decreases, and the ratio of the target power Pw2 gradually increases. In the high speed region of v? vb, the target power Pw1 is set to 0 and the target power Pw2 is set to the maximum (= Pw0). Based on this set characteristic, the target power calculating unit 58 calculates the target powers Pw1 and Pw2 according to the vehicle speed v and the accelerator pedal operation amount A, and predetermined target powers Pw1 and Pw2, respectively. It outputs to the value calculating part 54 and the torque calculating part 53. As shown in FIG.

In the torque calculating section 53, the relationship between the target torque T of the electric motor 23, the rotation speed Nm of the motor 23, and the power Pw2 is stored in advance. The current motor rotation speed Nm is grasped by the controller itself, and the torque calculating unit 53 is the target torque T corresponding to the target power Pw2 and the motor rotation speed Nm based on the characteristics shown. ) Is calculated. Then, the electric motor 23 controls the inverter 24 to output the target torque T. As a result, the power Pw2 of the electric motor 23 becomes a value set by the target power calculating unit 58.

When a part of the engine output is taken out as the power Pw2 of the electric motor 23 in this manner, the remainder is distributed to the HST, and the power Pw1 of the HST is set to the target power Pw1 set by the target power calculation unit 58. ) In the predetermined value calculating section 54, the relationship between the target power Pw1 and the predetermined value Pa is stored in advance. The predetermined value calculation unit 54 calculates a predetermined value Pa corresponding to the target power Pw1 based on this relationship, and outputs a control signal to the solenoid 12b of the hydraulic motor 12. This controls the predetermined value Pa.

The relationship between the HST traction force Fb of FIG. 5B and the HST target power Pw1 of FIG. 6 will be described. FIG. 7: is a figure which shows the relationship between HST traction force Fb and HST power Pw1, and b1 is the same characteristic as what was shown to FIG. 5 (b). B11 to b14 in FIG. 7 each have a constant power curve, and have a relationship of b11> b12> b13> b14. Since the power Pw1 is constant in the range of the vehicle speed v <va (FIG. 6), the traction force Fb changes along the curve b11 in which the power is constant. Since the power Pw1 gradually decreases when the vehicle speed exceeds va, the traction force Fb transitions from the point P11 on the curve b11 to the point P12 on the curve b12 → the point P13 on the curve b13 → the point P14 on the curve b14. As a result, the characteristic of the pulling force Fb of FIG. 5 (b) is obtained from the characteristic of the power Pw1 of FIG.

An example of the operation of the traveling drive apparatus according to the first embodiment will be described.

When the accelerator pedal is depressed to the maximum when the vehicle starts, the hydraulic oil is supplied from the hydraulic pump 11 to the hydraulic motor 12, and the front wheel 113 is driven by the HST. The electric motor 23 rotates in response to the signal from the inverter 24, and the rear wheel 123 is driven by the electric motor 23. At this time, the engine output is distributed to the HST and the electric motor 23, but until the vehicle speed v reaches a predetermined value va, as shown in FIG. 6, the power Pw1 distributed to the HST is the electric motor 23. ) Is larger than the power Pw2 distributed in the following manner (Pw1> Pw2). For this reason, HST acts effectively, and as shown in FIG. 5, the running performance of high pull force is obtained at low speed.

In the region where the vehicle speed v is not less than va and vb, as the vehicle speed v becomes faster, the power Pw2 distributed to the electric motor 23 increases, and the power Pw1 distributed to the HST decreases. When the vehicle speed v is equal to or higher than vb (= v2), Pw1 = 0 and the pump tilt angle qp becomes zero. Thereby, as shown in FIG. 5, traction force Fb becomes zero and the running performance of a high speed low pull force is obtained. In this case, the vehicle is towed by only the pulling force Fc of the electric motor 23. For this reason, since it is not necessary to drive a vehicle at high speed by HST, the power loss in the HST drive device at the time of high speed driving becomes small, and fuel economy can be improved.

According to the above first embodiment, the following effects can be achieved.

(1) The front wheel 113 is driven by the HST driving drive device and the rear wheel 123 is driven by the electric motor 23, and in the region where the vehicle speed v is va or more and vb or less, the vehicle speed v As the increase, the power Pw1 distributed to the HST decreases with the vehicle speed, and when the vehicle speed v becomes larger than vb, Pw1 = 0. As a result, when the vehicle speed is at a high speed of v2 or more, only the traction force Fc of the electric motor 23 acts on the vehicle, thereby reducing the power loss of the HST drive device and improving fuel economy.

(2) Since the rear wheels 123 are driven by the electric motor 23, a large traction force Fa can be obtained as the whole vehicle. For this reason, the pump 11 and the motor 12 of the HST can be miniaturized as compared with obtaining the traction force Fa only by the HST.

(3) The operation amount A of the accelerator pedal is detected by the operation amount detector 52, and the larger the operation amount A is, the greater the power Pw1 of the HST and the power Pw2 of the electric motor 23 are ( 6, the engine output can be efficiently distributed to the HST and the electric motor 23 at all times.

(4) Since the front wheel 113 having a large load acting on the axle was driven by the HST, and the rear wheel 123 having a small axial load was driven by the electric motor 23, the traction force by the electric motor 23 was obtained. (Fc) may be small, and an optimal traveling system can be constructed by the HST and the electric motor 23.

(5) When the distribution of the power Pw1 is changed in accordance with the vehicle speed v, the controller 50 automatically changes to the pump tilt angle qp and the motor tilt angle qm corresponding to the power Pw1. ), It is not necessary to directly control the tilt angles qp and qm, and the configuration is easy.

Second Embodiment

With reference to FIG. 8, 9, 2nd Embodiment of the drive system which concerns on this invention is described.

In the second embodiment, a generator motor is provided instead of the electric motor 23 as the rear wheel drive device 20 to recover the kinetic energy of the vehicle at the time of deceleration. 8 is a diagram illustrating a configuration of a traveling drive device according to a second embodiment. In addition, the same code | symbol is attached | subjected to the same part as FIG. 2, and the difference is mainly demonstrated below.

 In addition to the vehicle speed detector 51 and the accelerator operation amount detector 52, the operation amount detector 57 for detecting the operation amount B of the brake pedal is connected to the controller 50. The controller 50 subtracts the manipulated value B of the manipulated variable detector 57 from the manipulated value A of the manipulated variable detector 52, and outputs an acceleration command if the subtracted value is positive and a deceleration command if negative. When the acceleration command is output, the generator motor 55 functions as an electric motor, and when the deceleration command is output, it functions as a generator. In addition, a work pump is connected to the engine output shaft of the wheel loader, and the accelerator pedal is operated to adjust work horsepower during work. For this reason, in an industrial vehicle such as a wheel loader, the accelerator pedal and the brake pedal may be operated simultaneously.

When the generator motor 55 functions as an electric motor, the drive current according to the control signal from the controller 50 is supplied to the generator motor 55 via the inverter / converter 56, and the generator motor 55 is driven. do. This point is the same as that of the first embodiment. For example, when the brake pedal is not operated, the power Pw2 of the generator motor 55 is the accelerator pedal operation amount A and the vehicle speed ( changes according to v). When the generator motor 55 functions as a generator, the electric power generated by the generator motor 55 is charged to the battery 22 via the inverter / converter 56.

9 (a) to 9 (c) are diagrams showing the relationship between the vehicle speed v and the traction force F in the second embodiment, and FIGS. 5 (a) to 5 (c) of the first embodiment respectively. Corresponds to. When the deceleration command (brake command) is output when the vehicle runs, the generator motor 55 functions as a generator, so the traction force Fc becomes negative, and the brake force acts on the vehicle. As a result, the kinetic energy at the time of deceleration can be recovered by the battery 22. In this case, as the deceleration command value is larger, the amount of power generation increases and the brake force increases. When the vehicle speed v is lowered, the hydraulic brake by the HST is operated simultaneously. In this case, first, the brake by the generator motor 55 is operated, and if it is still insufficient, the hydraulic brake by the HST is operated. By doing so, power is generated preferentially by the generator motor 55, so that the kinetic energy can be efficiently recovered.

As described above, according to the second embodiment, since the rear motor 123 is driven by the generator motor 55 and generated at the time of deceleration, kinetic energy that is unnecessary at the time of deceleration can be recovered as electrical energy. It can improve fuel economy. The operation amount A of the accelerator pedal and the operation amount B of the brake pedal are detected, the deceleration command is determined by the difference between the operation amounts A and B, and the larger the deceleration command value is, the more the generator motor 55 Since the amount of power generation is increased and the brake force is increased, a suitable brake force can be given to the vehicle.

Moreover, in the said embodiment, although the brake force is applied to a vehicle by using the motor generator 55 as a motor generator as a generator, what is called a mechanical brake which drives a brake disk and exerts a brake force may be used together. Although the acceleration / deceleration instruction is determined by the controller 50 from the difference between the operation amount A of the accelerator pedal and the operation amount B of the brake pedal, the determination unit is not limited to this.

Although the HST hydraulic circuit is formed so as to mechanically change the pump tilt angle qp and the motor tilt angle qm of the HST traveling drive device, the tilt angles qp and qm may be directly controlled by electronic control. The front wheels 113 serving as the first driving wheels were driven by the HST, and the rear wheels 123 serving as the second driving wheels were driven by the electric motor 23, but the front wheels 113 were driven by the electric motors 23 and the rear wheels 123. ) May be driven by HST, and the combination of the driving methods of the wheels 113 and 123 is not limited to the above. Although the manipulated-variable A of the accelerator pedal was detected by the manipulated-variable detector 52, other acceleration detection units may be used.

In the low speed region where the vehicle speed v detected by the vehicle speed detector 51 is va (first predetermined value), the power Pw1 (first power) of the HST is changed to Pw2 (second power) of the electric motor 23. In the medium speed region of va <v <vb (second predetermined value), Pw1 is gradually decreased and PW2 is gradually increased, and in the high speed region of v ≥ vb, Pw1 is zero. Although Pw2 is made maximum (Pw0) (FIG. 6), as the vehicle speed v increases, the ratio of the power distributed to the HST decreases, so that the ratio of the power distributed to the electric motor 23 increases. If the engine output is distributed to the HST and the electric motor 23, the configuration of the controller 50 as the controller is not limited to the above. Accordingly, the characteristics of the traction forces Fa to Fc are also not limited to those shown in FIGS. 5 and 9. If the output torque T of the electric motor 23 is controlled so that the vehicle speed v2 when the traction force Fb becomes zero and the vehicle speed v2 when the traction force Fc starts to decrease (Fig. 5) The configuration of the controller 50 as the torque control unit may be any.

Although the above embodiment is applied to a wheel loader, the present invention is similarly applicable to other work vehicles (for example, wheel type hydraulic excavators). That is, the present invention is not limited to the traveling drive device of the embodiment as long as the features and functions of the present invention can be realized.

This application is based on Japanese Patent Application No. 2006-326694 (filed December 4, 2006), the contents of which are incorporated herein by reference.

Claims (10)

An HST drive having a hydraulic pump driven by a prime mover and a hydraulic motor connected to the hydraulic pump in a closed loop; An electric motor driven using electric power generated by the driving of the prime mover, A first driving wheel driven by the HST driving device; A second driving wheel driven by the electric motor, A vehicle speed detector for detecting a vehicle speed; As the vehicle speed detected by the vehicle speed detector increases, the ratio of the first power to be distributed to the HST drive is reduced, and the ratio of the second power to be distributed to the electric motor is increased so that the output of the prime mover is increased. And a control unit for distributing the HST drive unit and the electric motor. An HST drive having a hydraulic pump driven by a prime mover and a hydraulic motor connected to the hydraulic pump in a closed loop; A motor generator driven by using electric power generated by the driving of the prime mover, functioning as an electric motor, and driven by kinetic energy at the time of driving, and functioning as a generator; A first driving wheel driven by the HST driving device; A second drive wheel driven by the motor generator, A vehicle speed detector for detecting a vehicle speed; A judging section which determines the output of the acceleration / deceleration command of the vehicle, If it is determined that the acceleration command is outputted by the determination unit, the motor generator functions as an electric motor, and as the vehicle speed detected by the vehicle speed detection unit increases, the ratio of the first power to be distributed to the HST drive unit is increased. To distribute the output of the prime mover to the HST drive and the motor generator so that the ratio of the second power distributed to the motor generator is increased And a control unit for causing the motor generator to function as a generator when it is determined that the deceleration command is output by the determination unit. The method of claim 2, And the control unit increases the amount of power generated by the motor generator when the deceleration command value is output by the determination unit. The method according to any one of claims 1 to 3, An acceleration detection unit for detecting an acceleration command value; And the control unit distributes the power of the prime mover to the HST drive unit and the electric motor so that the first power and the second power increase as the acceleration command value increases. The method according to any one of claims 1 to 4, And said first driving wheel is a front wheel, and said second driving wheel is a rear wheel. The method according to any one of claims 1 to 5, The control unit, When the vehicle speed detected by the vehicle speed detection unit is within a first predetermined value or less, the ratio of the first power is controlled at a constant ratio larger than the ratio of the second power, In a range in which the vehicle speed detected by the vehicle speed detection unit is larger than the first predetermined value and smaller than the second predetermined value larger than the first predetermined value, the ratio of the first power is gradually decreased, And the ratio of the first power is zero when the vehicle speed detected by the vehicle speed detector is equal to or greater than the second predetermined value. The method according to any one of claims 1 to 6, And a gear mechanism for transmitting power from the HST drive device to the first drive wheels. The method according to any one of claims 1 to 7, The control unit maintains a constant output torque of the electric motor until the traction force by the HST drive becomes 0, and after the traction force by the HST drive becomes 0 by increasing the vehicle speed, And a torque control unit for controlling the output torque of the electric motor so as to initiate a decrease in traction force. A work vehicle comprising the traveling drive device according to any one of claims 1 to 8. It has a hydraulic pump driven by the prime mover and the HST drive device which connected the hydraulic motor to the closed circuit, and this HST drive device drives a 1st drive wheel, Drive the second drive wheel by the electric motor, And increasing the ratio of the first power distributed to the HST drive device and increasing the ratio of the second power distributed to the electric motor as the vehicle speed increases.

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